1. Field of the Invention
The field of art to which this invention pertains is the solid bed adsorptive separation of terpenoids. More specifically, the invention relates to a process for separating monoterpene alcohols from a feed mixture comprising monoterpene alcohols, and monoterpene aldehydes and/or ketones by adsorptive separation using crystalline aluminosilicate adsorbents.
2. Background Information
The use of crystalline aluminosilicates to perform hydrocarbon separation is well known in the separation art. Examples of such separations are disclosed in U.S. Pat. Nos. 2,985,589 and 3,201,491 wherein a type A zeolite is used to separate normal paraffins from branched chain paraffins. The use of faujasites to separate olefinic hydrocarbons from paraffinic hydrocarbons is described in U.S. Pat. Nos. 3,265,750 and 3,510,423. These adsorbents allow a separation based on the physical size differences in the molecules by allowing the smaller or normal hydrocarbons to be passed into the cavities within the zeolitic adsorbent, while excluding the larger or branched chain molecules.
In addition to being used in processes for separating hydrocarbon types, adsorbents comprising type X or Y zeolites have also been employed in processes to separate individual hydrocarbon isomers. In the processes described, for example, in U.S. Pat. Nos. 3,626,020 to Neuzil, 3,663,638 to Neuzil, 3,665,046 to deRosset, 3,668,266 to Chen et al., 3,686,343 to Bearden Jr. et al., 3,700,744 to Berger et al., 3,734,974 to Neuzil, 3,894,109 to Rosback, 3,997,620 to Neuzil and B 426,274 Hedge, particular zeolitic adsorbents are used to separate the para isomer of bialkyl substituted monocyclic aromatics from the other isomers, particularly paraxylene from other xylene isomers.
Turning specifically to the class of compounds of this invention, terpenoids include the saturated or partially saturated isomers of terpenes as well as derivatives such as alcohols, ketones, aldehydes, esters, etc. Terpenes are chiefly derived from essential oils. The oxygenated terpenoid derivatives are particularly important flavor and perfume materials. Most commonly used terpenes are separated by fractional distillation. However, terpene compounds are heat sensitive, thus fractionation often requires energy intensive vacuum distillation techniques to avoid degradation of components.
Apart from fractionation, adsorptive separation techniques have been used to isolate individual terpenes from essential oils and other terpene containing feedstocks. U.S. Pat. No. 2,760,993 teaches the use of activated clay, magnesia, charcoal and alumina in conjunction with polar solvents to separate menthol from mint oils. Preparation of a terpeneless essential oil by removal of terpenes through distillation and adsorption onto neutral alumina is taught in U.S. Pat. No. 3,867,262.
Applicant has found that monoterpenoids can be separated by adsorptive separation techniques using an X-type zeolite.